The Cubs have told starting shortstop Ryan Theriot to start working out second base, in preparation for top prospect Starlin Castro taking over at shortstop at some point next season.

While there are no guarantees that Castro will see time at Wrigley in 2010, he certainly has shown he has what it takes by hitting .299 in 127 games between High-A and Double-A with 29 extra-base hits, 28 stolen bases, and K/BB of 53/29, and a .342 on-base percentage. He followed his breakout season with a .376 average in 26 games in the AFL. 

If Theriot expects to remain in the league long-term, a move to second is essential. He does not have a strong enough arm for shortstop, despite putting up an above average UZR/150 of 8.3. If he can continue to hit between .280-.300, he should be able to hold down a position in the Cubs infield for some time.

This is definitely a cost-saving move for the Cubs down the road. The Cubs are expected to add an outfielder this offseason, but that move hinges on when and for who they trade Milton Bradley for. Beyond that, the Cubs seem committed to developing their minor league system, where they have young pitchers who appear ready to contribute and lower-level bats who are on the verge of reaching some of the tougher levels. 

Free agent shortstop Orlando Cabrera could be a target for the Cubs on a one-year deal, giving the Cubs the option to either trade him midseason or collect draft picks on him after the 2010 season. After hitting .282 with 9 home runs for the A's and Twins, he could receive an annual salary around 5 million dollars. 

In the event that the Cubs don't make a move for a middle infielder, expect to see the Cubs work a middle infield tandem with Ryan Theriot, Jeff Baker, Mike Fontenot, Andres Blanco, Aaron Miles, Bobby Scales, and maybe even Darwin Barney.